This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For the flux measurements of molecules that are not electrochemically active, we have been employing enzymes for self-referencing electrodes. For example, among various enzyme types, the use of oxidases is favored as they produce electrochemically detectable hydrogen peroxide as a result of enzymatic oxidation in the presence of oxygen. In addition we have generated preliminary data on a design simplification using ceramic sol-gel matrices for encapsulation of materials.